1. Field of the Invention
This invention relates to an image and sound recording apparatus and more particularly to a sound recording method for the apparatus.
2. Description of the Related Art
Among image recording apparatuses of the kind recording sounds as well as images in concentric circular recording tracks on a magnetic sheet with one field portion of a video signal recorded in each of the tracks, some of them are arranged to record a time-compressed audio signal along with the video signal in proper correlation to the video signal on the same magnetic sheet; to add to the audio signal some data concerning the track numbers of tracks in which the correlated portions of the video signal are recorded and the time-base compression rate of the audio signal; and to record the audio signal with the data in tracks other than the video signal recording tracks.
In reproducing from the magnetic sheet the signals recorded by the recording apparatus in the above stated manner, the audio signal is time-expanded and the video signal corresponding to the audio signal is reproduced in accordance with the data added. Generally, the audio signal is time-compressed at one of three different rates, i.e. compressed by 320 times, 640 times or 1280 times, and the real time of the audio signal to be recorded and reproduced is about 5 sec, 10 sec or 20 sec.
It is possible to record the audio signal for about 5 to 20 sec in one track. However, a quite impractical occasion arrises when one audio signal recording track is correlated to one video signal track, because in cases where image recording is arranged to be continuously performed at a rate of 0.5 sec per frame (i.e. two frames/sec), for example, each time one field portion of a field-recording video signal or two field portions of a frame-recording video signal is recorded, it would be an audio signal portion of only 0.5 sec that is recorded in one track, while the track has a capacity for recording the audio signal for a period of 5 to 20 sec. Therefore, only 1/10 of the audio signal recording capacity is actually used for sound recording.
Further, let us assume that a time-compressed audio signal is recorded in a suitable vacant track in recording an image and a sound relative to the image on a magnetic sheet. Then, in reproducing the record, if the magnetic sheet is loaded on a reproducing apparatus which is capable of only reproducing video signals, there arises the following problem: In case each of the records of the tracks is to be reproduced one by one to have, for example, the recorded images continuously monitored by feeding the tracks at a high speed, the tracks containing the audio signal are prone to be mistaken for the video signal tracks during the reproducing operation. This results in very unnatural reproduced images. This problem can be solved by muting the mistakenly reproduced audio signal output before it is supplied to an image monitor. Such a solution, however, presents another problem in that the reproduced image motion becomes unnatural due to discontinuity in the reproduction of the recorded images.
The above stated problems have been not limited to the recording apparatuses of the kind forming concentric circular recording tracks on a magnetic sheet but have arisen also in recording apparatuses of other kinds, such as the kinds using a plate shaped recording medium and a tape shaped recording medium.